Human Driven Changes in Atmospheric Aerosol Composition

Abstract

A set of global 3-dimensional model simulations have been performed to investigate the changes in atmospheric composition driven by humans. Sensitivity simulations using past, present and future anthropogenic emissions of pollutants are analyzed to derive the importance of human-driven emissions of pollutants for aerosol composition, including aerosol water, and for dust aerosol aging. The results show that applied emission control has significantly limited air pollution levels compared to a hypothetical uncontrolled situation. They also point out that human activities have increased atmospheric acidity and as a result the solubility of nutrients, like iron and phosphorus, in atmospheric deposition.

Questions and Answers

Questioner: Dick Derwent

Question: It is not an easy task to produce historic global emission inventories. Have you checked your predictions of ozone as surface sites with the baseline ozone observations collected by NOAA Boulder (Parrish et al. 2014) showing the growth from 1950 to 2000s followed by a levelling OH?

Answer: Indeed, historic emission inventories are difficult to be constructed. Therefore, in our study we use what is widely used by the modeling community, the anthropogenic emissions inventories: the historical Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) database for the year 1850 and for the years 1980–2000 that has been constructed by Lamarque et al. (Geosci. Model Dev., 6, 179–206, 2013). For the years after 2000, we use the Representative Concentration Pathway 6.0 (RCP 6.0) emission scenario developed by van Vuuren et al. (Clim. Change, 109, 5–31, 2011). With regard to model evaluation we have compared with all available surface data without however selecting only the baseline conditions as done in the Parrish et al. (JGR, doi:10.1002/2013JD021435, 2014) paper. The purpose of the comparison to observations was to evaluate the ability of the model to reproduce realistically the atmospheric concentrations. In this case a comparison with “baseline” measurements would not provide any additional information.

Questioner: Wanmin Gong

Question: Is your scenario where you keep per-capital energy consumption at 1980 level the worse-case scenario? It is difficult to untangle the increase in energy demand, new technology, and legislation impacts.

Answer: It should not be considered as the worst-case because it does not account for the increase in energy demand per capita since 1980. The worst-case scenario should account for stagnant technology i.e. for the same energy demand same constant per capita emissions and in addition account for the increase in energy demand per capita. While, there are statistics for the energy demand per capita, it is indeed very difficult to distinguish the impact of new technologies from that of legislation. The concept of our modeling study does not allow separating between new technology and legislation. However, it provides an alternative way to investigate the effectiveness of emission mitigation legislation.